Fuel pump power supply

[Calvin Tan]

I'm curious to know if your external fuel pump (only fitted on earlier E30 model) power supply same as mine.

When at idling 11.9volt
With A/C on at idling 11.6volt
With A/C + headlight + foglamp on at idling 11.0volt

Is that normal???

[arsevader]

I'm curious to know if your external fuel pump (only fitted on earlier E30 model) power supply same as mine.

When at idling 11.9volt
With A/C on at idling 11.6volt
With A/C + headlight + foglamp on at idling 11.0volt

Is that normal???

Nothing to do with the fuel pump, I assume you are just measuring the voltage at the pump from the power lead?

Sounds like your alternator can't keep up. What's your voltage at the battery when idling etc?

James

[Calvin Tan]

Nothing to do with the fuel pump, I assume you are just measuring the voltage at the pump from the power lead?

Sounds like your alternator can't keep up. What's your voltage at the battery when idling etc?

James

Yes, sorry I mean I'm measuring the power supply to the fuel pump.
My battery voltage at idling is 13.6volt without turning on A/C, headlamp and accessories. I'm using a brand new Bosch 115amp from E34 model.
What normally is the idling power supply to an E30 fuel pump?

[arsevader]

Yes, sorry I mean I'm measuring the power supply to the fuel pump.
My battery voltage at idling is 13.6volt without turning on A/C, headlamp and accessories. I'm using a brand new Bosch 115amp from E34 model.
What normally is the idling power supply to an E30 fuel pump?

I'm not sure but usually most things are getting battery voltage, not sure about the pump. But if your voltage drops that much I'd suspect the voltage regulator is weak.

James

[Calvin Tan]

I'm not sure but usually most things are getting battery voltage, not sure about the pump. But if your voltage drops that much I'd suspect the voltage regulator is weak.

James

But the voltage on the battery at idling is fine = 13.6v but when I measure on the fuel pump terminal is only 11.9v. When I ask my friend E36 M3 evo (his fuel pump located intank) he measure his fuel pump terminal is only 12.0v.
So I wonder is that normal? And I need more feedback, maybe you all can try and let us know....